There are a number of situations in which treatment of root canals in teeth is indicated. The tissue lying within the tooth structure, the dental pulp, may become diseased as a result of dental caries or the cells and tissue may be traumatised or atrophy. As a result of this, the pulp tissue may die and/or become infected. This leads to death of the pulp. While it has been common practice to extract the tooth, use of the tooth can be preserved by the removal of the diseased tissue and sealing the cleaned and sterilised canal. The operation of mechanically removing the diseased pulp is technically difficult and require the accessing of the canal and removing infected tissue, which may be at or near the apex of the root of the tooth. The treatment becomes more complex as the anatomy of the root canal becomes more complex and the canals themselves become narrower.
Conventional endodontic treatment involves first gaining access to the pulp chamber by removing the overlying enamel and dentine. Once the pulp chamber is exposed, the entrances to the root canals are then located and enlarged. The length of the root canal is calculated from a diagnostic radiograph or by means of an apex locator and the canal is instrumented using files and/or reamers of increasing size. These instruments are designed to remove the internal surface of the root canal by rasping and cutting the dentine walls. The dentine walls have small holes where the dentine forming cell processes track into the dentine. These holes are sites where bacteria can settle and proliferate. It is these areas which are reduced by mechanical debriding of the internal surface of the root canal. To achieve this, the reamers and files are used to produce a root canal that, near the apex, is matched in size to the obturating device. The internal diameter of the canal is enlarged so that the cavities in the root wall are reduced in size and the canal is mechanically cleaned.
Medicaments may be used to chemically kill the bacteria; these are usually disinfectants and anti-bacterials such as hypochlorite solution or antibiotic pastes. These may be introduced into the root canal after initial mechanical debridement. These medicaments and mechanical methods of removal of tissue are designed to produce a root canal which is free of bacteria and other contaminants. Conventional procedures are time consuming and difficult to carry out since they require careful and extensive mechanical debridement of the canal walls and use of copious volumes of irrigants such as aqueous sodium hypochlorite to flush out the canal. The more posterior the tooth situation within the mouth the greater the risk of failure to achieve the objectives, since the root canals morphology becomes more convoluted and adequate access becomes more difficult to achieve.